Electron mobility in graphene without invoking the Dirac equation

Ullal, Chaitanya K.; Shi, Jian; Sundararaman, Ravishankar

doi:10.1119/1.5092453

Cited by 15 publications

(14 citation statements)

References 13 publications

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“…Of crucial importance includes reducing the conduction channel length and preventing the surface from unintentional doping, which should be achievable with the recent development of lithography techniques and capping of topological insulator with atomically precise interface [18]. The extremely high mobility would be achievable, whose significance can be invoked from the isotropic mobility formula for Dirac electrons [47],…”

mentioning

confidence: 99%

Accessing the Intrinsic Spin Transport in a Topological Insulator by Controlling the Crossover of Bulk-to-Surface Conductance

Nguyen

Kim

et al. 2018

Phys. Rev. Lett.

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We report a method to control contributions of bulk and surface states in topological insulator Bi 2 Te 2 Se that allows accessing the spin-polarized transport endowed by topological surface states. An intrinsic surface dominant transport is established when cooling the sample to low temperature or reducing the conduction channel length, both achieved in situ in the transport measurements with a four-probe scanning tunneling microscope without the need of further tailoring the sample. The topological surface states show characteristic transport behaviors with mobility about an order of magnitude higher than reported before, and a spin polarization approaching theoretically predicted value. Our result demonstrates accessibility to the intrinsic high mobility spin transport of topological surface states, which paves a way to realizing topological spintronic devices.

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mentioning

confidence: 99%

Accessing the Intrinsic Spin Transport in a Topological Insulator by Controlling the Crossover of Bulk-to-Surface Conductance

Nguyen

Kim

et al. 2018

Phys. Rev. Lett.

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“…The effective mass as defined above can also be regarded as the inverse of the curvature of the band structure E(k). Now, naive application of the conventional above semiconductor definition of effective mass to linear dispersion given above reduces to (m * ) −1 = 0 or an infinite effective mass of Dirac fermions [17]. Then, how is it possible to account for the finite mass (zero or non-zero, if possible) of Dirac fermions.…”

Section: Calculation Of Effective Mass For Dirac-like Spectrummentioning

confidence: 99%

“…Besides, in fact there is no Lorentz invariance for charge carriers in graphene. The problem of effective mass can be answered clearly if we think that the effective mass is indeed a second rank tensor [(m * ) −1 ] ij = 1 2 ∇ i ∇ j E(k) and can be written more compactly for 2d graphene system [17] as…”

Section: Calculation Of Effective Mass For Dirac-like Spectrummentioning

confidence: 99%

“…In this case, the topology of the Dirac point and Pauli exclusion principle dictate [17] that the transverse mass…”

Section: Calculation Of Effective Mass For Dirac-like Spectrummentioning

confidence: 99%

“…Furthermore, his equation has successfully introduced the brilliant idea of quantum field theory. However, the discovery of graphene [14,15] surprisingly triggered the question regarding the relevance of relativistic Dirac equation [17][18][19] in the field of material science.…”

Section: Introductionmentioning

confidence: 99%

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Dirac Materials in a MatrixWay

Bandyopadhyay¹,

Jana²

2020

ujms

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Recent years have been the platform of discovery of a wide range of materials, like d-wave superconductors, graphene, and topological insulators. These materials do indeed share a fundamental similarity in their low-energy spectra namely the fermionic excitations. There carriers behave as massless Dirac particles rather than conventional fermions that obey the usual Schrödinger Hamiltonian. A surprising aspect of most Dirac materials is that many of their physical properties measured in experiments can be understood at the non-interacting level. In spite of the large effective coupling constant in case of graphene, it has been observed that the interactions do not seem to play a major key role. Controlling the electrons at Dirac nodes in the first Brillouin zone needs the interplay of sublattice symmetry, inversion symmetry and the time-reversal symmetry. In this article, we have used explicit fundamental symmetry to understand the basic features of Dirac materials occurring in three diverse systems in a compact 2 × 2 matrix way. Furthermore, the robustness of the Dirac cones has also been explored from the scientific notion of topological physics. In addition, an elementary introduction on the three dimensional (3D) topological insulators and d wave superconductors will shed light in their respective fields. Furthermore, we have also discussed the way to evaluate the effective mass tensor of the carriers in the two dimensional (2D) Dirac materials. This methodology has also been critically extended to three dimensional (3D) topological insulators and d wave superconductors.

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Smith–Purcell Radiation from Highly Mobile Carriers in 2D Quantum Materials

Nussupbekov

Xiong

et al. 2023

Laser & Photonics Reviews

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Terahertz (THz) radiation has broad applications ranging from medical imaging to spectroscopy. One viable source of high‐intensity THz radiation is the Smith–Purcell (SP) effect, which involves charge carriers moving over a periodic surface. Conventional SP emitters use electron beams to generate charge carriers, necessitating bulky electron acceleration stages. Here, a compact design for generating THz SP radiation using mobile charge carriers within 2D materials is proposed. This circumvents the beam alignment and beam divergence challenge, allowing for a reduction in the electron‐grating separation from tens of nm to 5 nm or less, leading to more efficient near‐field excitation and a potentially chip‐level THz source. In such a configuration, it is shown that the optimal electron velocity and the corresponding maximum radiation intensity can be predicted from the electron‐grating separation. The numerical demonstration shows that hot electrons can excite SP radiation in graphene on a silicon grating, and the radiation intensity can be increased by graphene surface plasmons. This study can be extended to a broad variety of charge carriers in 2D materials, thus allowing for compact, tunable, and low‐cost THz sources.

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Electron mobility in graphene without invoking the Dirac equation

Cited by 15 publications

References 13 publications

Accessing the Intrinsic Spin Transport in a Topological Insulator by Controlling the Crossover of Bulk-to-Surface Conductance

Accessing the Intrinsic Spin Transport in a Topological Insulator by Controlling the Crossover of Bulk-to-Surface Conductance

Dirac Materials in a MatrixWay

Smith–Purcell Radiation from Highly Mobile Carriers in 2D Quantum Materials

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